Radical-mediated regiodivergent C(sp3)–H functionalization of N-substituted indolines via enzymatic carbene transfer

Indolines are ubiquitous structural motifs occurring in pharmaceuticals and natural products. Here, we report a strategy for regio- and stereoselective C(sp³)–H functionalization of N-substituted indolines via carbene transfer chemistry mediated by engineered CYP119-based catalysts. These systems offer high enantioselectivity and high catalytic efficiency, as well as regiodivergent selectivity, furnishing an efficient and convenient route for diversification of these important scaffolds via direct C(sp³)–H functionalization. Selective functionalization of exocyclic C(sp³)–H bond in N-methyl indolines was also achieved, and a biocatalytic cascade combining enzyme-mediated α- and β-C(sp³)–H functionalization yielded a polycyclic indoline-containing motif found in drugs. Mechanistic and computational studies support a radical-mediated C–H functionalization pathway and provide insights into protein-mediated regiodivergent selectivity. Altogether, this work offers a direct and tunable strategy to access functionalized indolines as key building blocks for medicinal chemistry and natural product synthesis and provides first insights into the mechanism of P450-catalyzed C(sp³)–H carbene insertion.